1. Field of the Invention
The present invention relates generally to the field of wireless telephone networks, devices, and related services such as voice mail. More particularly, the invention relates to mobility gateways which facilitate communication for wireless subscriber units in different networks, such as ANSI-41 and GSM networks.
2. Description of the Related Art
Wireless services provided to customers in the United States are primarily based on a standard known as American National Standards Institute (ANSI) 41. Wireless services provided to customers in Europe and a few non-European countries are primarily based upon the Global System for Mobile (GSM) standard. The ANSI-41 and the GSM networks are currently connected through gateways. Networks implementing one of these two different standards generate call requests and other messages using different protocols. Among other functions, the connecting gateways translate call requests from the ANSI-41 protocol to the GSM protocol (and vice versa as appropriate) to facilitate the exchange of call requests between these two networks.
Unfortunately, current ANSI-41/GSM gateways are limited to functions such as translating and delivering call requests. In certain circumstances as described below, these gateways are unable to help implement cost effective methods for providing an ANSI-41 customer roaming within a GSM network with call forwarding and related telephone services available to the ANSI-41 customer while in the ANSI-41 network.
One example of call forwarding use which is frequently selected by ANSI-41 customers is voice mail. When an ANSI-41 customer with voice mail is within the ANSI-41 network and unavailable to answer an incoming telephone call (either because the ANSI-41 customer's wireless telephone is inactive, or because the ANSI-41 customer's line is busy or not answered), the incoming call request is redirected to a forwarding telephone number which accesses the ANSI-41 customer's voice mail system. The voice mail system enables the calling party to leave an audio message for the ANSI-41 customer. Thus, voice mail services provide the ANSI-41 customer with an opportunity to identify and contact previous callers.
Unfortunately, if the ANSI-41 customer with voice mail is roaming within a GSM network and is unavailable to answer an incoming call, the availability of the ANSI-41 customer's voice mail service depends upon the reason why the ANSI-41 customer is unavailable. For example, suppose an ANSI-41 customer takes their wireless telephone to Europe and a caller in the United States uses a telephone connected to the public switched telephone network (PSTN) to place a call to the ANSI-41 customer. Once the ANSI-41 network receives the call request from the PSTN and determines the intended ANSI-41 customer is located in Europe, the ANSI-41 network forwards the call request through an ANSI-41/GSM gateway to the ANSI-41 customer in Europe.
If the ANSI-41 customer's wireless telephone is inactive, current GSM networks are able to indicate the wireless telephone's inactive status to the ANSI-41 network via the ANSI-41/GSM gateway before the call itself is forwarded to the GSM network. In this case, there are known cost-effective methods for efficiently forwarding the incoming call to the ANSI-41 customer's voice mail system so that the calling party can leave a message. These known methods are cost effective because only local telephone calls and corresponding local telephone charges are involved for the calling party.
If the ANSI-41 customer's wireless telephone is active and the customer is available to answer the telephone, the call is completed in accordance with the call request and call forwarding type services are not implemented. However, if the ANSI-41 customer's wireless telephone is active and the telephone is either busy or not answered, current GSM networks are unable to indicate this wireless telephone status information to the ANSI-41 network. If current GSM networks were able to indicate this wireless telephone status information to the ANSI-41 network, then this situation could be handled in a manner similar to the known methods for handling the situation described above.
However, because current GSM networks are not designed to include the ability to indicate to the ANSI-41 network when a call to a wireless telephone goes unanswered or when the wireless telephone is busy, one of two different scenarios are likely to occur: (1) the calling party receives a message indicating the ANSI-41 customer is “out of network,” the ANSI-41 customer receives a message indicating a call was missed, and no mechanism is provided which allows the calling party to access the ANSI-41 customer's voice mail service; or (2) the GSM network, having received the call, forwards the call from the GSM network to the ANSI-41 customer's voice mail service via the ANSI-41 network without indicating status information to the ANSI-41 network.
Unfortunately, both of the above two scenarios have drawbacks. With the first scenario, the message received by the ANSI-41 customer does not enable the ANSI-41 customer to identify the calling party. With the second scenario, the calling party is able to identify him/her self to the ANSI-41 customer, but this method is not cost effective because the calling party is charged for two long distance international calls. The first international call charge results from the original call path from the ANSI-41 network to the GSM network in Europe, and the second international call charge results when the GSM network forwards the first call path back to the ANSI-41 network to establish a connection to the ANSI-41 customer's voice mail service.